How Many Calories to Lose 1 kg Per Week (Safely)?

If you've ever typed "calories to lose 1 kg per week" into Google, you've probably seen the same number thrown around: 7,700 kcal per kilogram of body fat. Divide by seven days and you get about 1,100 kcal per day of deficit.

That number is technically correct. In practice, it's almost never the right target. Here's why — and what to do instead.

The 7,700 kcal rule (where it comes from)

The original estimate traces back to nutrition researcher Max Wishnofsky in 1958: he calculated that one pound of fat stores about 3,500 kilocalories. Scaled to metric, that's 7,700 kcal per kilogram. Modern reviews put the real number slightly lower (~7,200 kcal) once you account for water and lean tissue, but 7,700 is still the working rule.

So to burn 1 kg of pure fat in 7 days:

• 7,700 kcal ÷ 7 days ≈ 1,100 kcal/day deficit

The 1 kg/week problem

For most people, a 1,100 kcal/day deficit is too steep:

• A moderately active 70 kg woman needs about 2,200 kcal/day to maintain. A 1,100 kcal/day cut drops her to 1,100 kcal/day — below the safe-floor guidance most clinicians use (≈1,200 kcal for adult women).
• Aggressive deficits amplify muscle loss if protein or resistance training is low.
• Adherence plummets. A deficit you can't hold for 12 weeks is worse than a smaller one you can hold for 30.

The 0.5 kg/week sweet spot

The 500 kcal/day deficit — roughly 0.5 kg/week — is the number most registered dietitians land on. It:

• Keeps you above the safe floor for almost every adult.
• Preserves lean mass when paired with 1.6–2.2 g/kg protein.
• Lets you eat real meals — not 1,100 kcal of chicken and broccoli.

If you run our calorie deficit calculator you'll see this is where the safe-rate band lives by default.

Fast table: your daily calorie cut

| Weekly goal | Daily deficit | Time to lose 5 kg | | --- | --- | --- | | 0.25 kg | ~275 kcal | ~20 weeks | | 0.5 kg | ~550 kcal | ~10 weeks | | 0.75 kg | ~825 kcal | ~7 weeks | | 1 kg | ~1,100 kcal | 5 weeks |

What this looks like in food

Rough conversions for a 500 kcal cut:

• One bottle of soft drink (~140 kcal) + one slice of pizza (~285 kcal) + one cappuccino with full-fat milk (~80 kcal).
• Or: 15-minute brisk walk (~80 kcal) + smaller dinner portion (~200 kcal) + one less snack (~200 kcal).

You don't need to eat less of everything. A 500 kcal deficit is a couple of small, consistent swaps a day — not a diet overhaul.

If you really do want 1 kg/week

You probably have a short window (a wedding, a shoot, a transformation month). Three guardrails:

1. Don't go below the floor. Women: 1,200 kcal. Men: 1,500 kcal.
2. Eat ~2 g/kg of protein. This is what protects your muscle mass.
3. Cap the duration. 4–6 weeks, then return to a smaller deficit or maintenance for an equal period.

Bottom line

The math says 1,100 kcal/day. The biology says aim for 500–700 kcal/day instead. Slower loss, better muscle retention, and an intake you can actually live with.

Run your numbers in the calorie deficit calculator — it'll cap suggestions at the safe floor automatically.